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[Red]

I just had to re-motor my 20 year old Seledkin. For ~8 years I've been running a Turnigy Gliderdrive 840kV with a 14x9.5 graupner prop and 4S3300 set up. It's worked very well indeed at warping spacetime and observer's minds.

A couple of weeks ago I had cause to recalibrate the controls using Mike Shellim's wonderful Calibrate Mode and at the end of the process went to check the motor arm and disarm and throttle behaviour. For the first time ever the motor did Very Odd Things, fortunately with the prop removed. It felt a bit stiff/notchy but another couple of tries made it seem happy, so I replaced the prop and tried a power run. Well, that went ok for about 2 seconds and then lots of nasty stuttering etc.

So I removed the nosecone, pulled the motor to look at it and even with now ESC attached it was hard to turn. So I dismantled the motor (the glider drive is an outrunnuner-in-a-can to keep wires out of the way in a tight nose) and it looked like one of the windings was damaged.Fortunately I had a spare bought 6 years ago for another model that sill hasn't been touched, so I swapped it in and tried a basic power up without the prop - all OK.

Since things were looking up I hopped over to the online ecalc to check the likely figures. One thing that has changed recently is a new set of batteries. I've been using the same set of tired turnigy nano-tech 4S3300 packs since 2017 and just got some Zeeeeee (how many 'e's?) 4S3700 packs. eCalc tells me I've been pulling 90+ amps through a 70A cheap ESC and a motor that doesn't want more than 70A either. It's so long ago that I have no memory of whether I check the original setup with eCalc, but maybe I just swapped the old and very worn Aveox F12G back the and kept the same prop without really worrying. Evidently the new packs pushed it over the edge, or perhaps it's been marginal for a while and just gave up. I know the feeling.

So I'll move down to a 13x7 for some testing, and I've made a dinky little nose inlet and NACA side outlet in the nosecone, and if I can get one for a bearable price I'll probably swap to a ventilate spinner some day. Perhaps some air will help. I'd love to make a tiny powered hatch - like a retract door - to open during power and close for gliding, but that nose is already full. Wish me luck!

Seledkin......old school cool!! Any pics to share. For those that don't know, this was THE high performance competition plane to have.

 

[timrowledge]

The only decent pic I can find -and it's not even my Seledkin! - is

https://www.rccanada.ca/rccforum/attachment.php?attachmentid=32834&d=1209689039

Fantastic plane. 2m span, 4 servo wing, plus T tail elevator & throttle. All carbon/glass hollow-moulded wings & tail. Three-piece wing, flaps in the centre section, ailerons outboard, all integral hinges with wipers. Nosecone to insert battery instead of taking off the wing - much nicer. Just room for 4S33/3700 lipos, though you could certainly run off smaller lighter ones. With the manufacturer recommended movements it is so easy to fly, stable, responsive, fast, slows to a crawl on crow.

This is my second one. The first I got in I think 1995(?) from the wonderful Bruce DeVisser, complete with the Aveox motor/ESC. I had to replace it almost as soon as I moved up to Vancouver Island because that one didn't have flaps (so no crow) and at the new flying club I landed far too long and crushed the centre section leading edge in end-of-runway gorse. A new centre was almost as expensive as a new model with flaps, so that's what I got. Of course, I almost immediately damaged the leading edge of the centre and had to work out how to repair it! That was 20 years ago and it still flies near perfectly. I keep looking but never seem to find anything as attractive.

 

[timrowledge]

Ooh! I just spotted an online mention - an old 1998 EFI issue. See page 6 & 7

https://rcbookcase.com/data/media/66/07electric_flight_international_july1998.pdf

 

[j ferguson]

I made this because of my fear of wrecking the better replica I'd built. It has a 20mm Carbon fiber fuselage. Everything else is mounted on 3D printed fixtures which are threaded on to the tube and can be adjusted longitudinally for CG. I finall worked up the nerve to try to fly it. I chose hand-launch and quicly discovered that this was a good way to get a torque-roll induced crash. Without significan power, it wouldn't fly for long and with, I'd get the roll. It looks like wing loading is the problem and since that cannot be fixed without either building lighter or diverging from the intent to make a flying replica of AeroVironemnt's SwithcBalde300.

It looks to me like a solution is to catapult launch. I'm thinking of the Wright brothers' system witha falling weight. If the weight only falls 8 feet, I'll only see at max 20 mph, and I think i need at least 30. I can multiply the fall by pulleys which with a big enough wieght ought to get the job done.
so an 8 foot tower and a 6 foot ramp is where I'm going.

I'd thought about bungees, but couldn't see a way to deliver the thrust except with maximum right at the start which might be hard on the plane.

Second photo is the replica - with landing gear. The runway at my new field is very smooth and it may be that I can run this up to the 30mph on the ground and rotate - hopefuly and fly.

 

[Doc J]

I made this because of my fear of wrecking the better replica I'd built. It has a 20mm Carbon fiber fuselage. Everything else is mounted on 3D printed fixtures which are threaded on to the tube and can be adjusted longitudinally for CG. I finall worked up the nerve to try to fly it. I chose hand-launch and quicly discovered that this was a good way to get a torque-roll induced crash. Without significan power, it wouldn't fly for long and with, I'd get the roll. It looks like wing loading is the problem and since that cannot be fixed without either building lighter or diverging from the intent to make a flying replica of AeroVironemnt's SwithcBalde300.

It looks to me like a solution is to catapult launch. I'm thinking of the Wright brothers' system witha falling weight. If the weight only falls 8 feet, I'll only see at max 20 mph, and I think i need at least 30. I can multiply the fall by pulleys which with a big enough wieght ought to get the job done.
so an 8 foot tower and a 6 foot ramp is where I'm going.

I'd thought about bungees, but couldn't see a way to deliver the thrust except with maximum right at the start which might be hard on the plane.

Second photo is the replica - with landing gear. The runway at my new field is very smooth and it may be that I can run this up to the 30mph on the ground and rotate - hopefuly and fly.

With the greatest of respect and admiration for all that investment in time, hard work, and obvious application of brainpower, why?

Dont we normally try hard to make our gliders - or power planes - as beautiful as possible?

There can be intrinsic beauty in mechanical structures, and I am quite sensitive to that, but in this case - again with great respect - in this project I dont find any.

What does get me though, is a huge curiosity to find out why someone such as you with an obvious mechancal bent and love of modelling should want to make something so weird that even if totally successful - with the design needed to fulfill the role - will have no hope of flying very well.

Again - I admire what you are doing, but I'm afraid I dont understand it.

Really I'm not decrying here or trying to put the project down, but can you give me a clue?

Cheers,

Doc.

 

[j ferguson]

DocJ, no offense taken. I think I did it because I thought it would be difficult, maybe impossible. Here are a couple of shots of an earlier more conventional project. airfoil is Gottingen 418 - center section of Fokker DVII upper wing. ribs cut on cnc router and assembled using 3d printed fixtures in photo - covered with 1/32 balsa. I started out with about 3 degrees angle of incidence which turne out to be way too much. none worked fine. flew very nicely bogth fast and quite slow. It was my other scratch design-build. ailerons driven by carbon fiber torque tubes from servos in fuselage.
I've been retired for 20 years. I spent most of my career struggling with problems I just barely understood mostly because we cojld never find anyone else who did.
so that's what i do now - things I just barely understand.

 

[j ferguson]

partially build wing. I thought I was going to need full length carbon fiber spars 10mm and 6mm, but it turned out to be so stiff when it was skinned that i was able to get by with 6 inch stubs. enough to engage 5 ribs iirc.

 

[j ferguson]

Hi Doc, maybe I didn't explain it well. The version with the 20mm tube was designed to be easy to rebuild post-crash. and it is.

 

[Doc J]

Hi Doc, maybe I didn't explain it well. The version with the 20mm tube was designed to be easy to rebuild post-crash. and it is.

Well, nothing wrong with a military spec.

I tend to go exactly the opposite way with the looks and the performance propositions for my models, which may perhaps be the reason why I dont fully understand your thinking.

But its interesting.

Cheers,

Doc.

 

[Yotaman1985]

Learned that you can change the power up sound on my Jeti radio last night. Had to do something fun...

 

[Doc J]

Learned that you can change the power up sound on my Jeti radio last night. Had to do something fun...

I dont think you have enough to do, Yo...

Doc.

 

[jure]

Learned that you can change the power up sound on my Jeti radio last night. Had to do something fun...

I would use this one

 

[j ferguson]

I use this. Earlier the first 16 bars of Fiesta in Brass 1944 Roy Eldridge

 

[Doc J]

Holy Moly...its infectious...

Doc.

 

[RafaelAvila]

Need a sign??

 

[G-man]

Lovely.
Very nicely done.

 

[thenated0g]

Saw that on your IG post, that looks great. Sign making is fun and lasers take all the irritating parts out.
Its been so hot up here (111f) i havent been motivated to do much.
Did cut out and work on a little virtual pinball test bench to see if i can get it working before moving to a more solid setup:


Also played music for the first time in front of people, went well.

 

[jakem]

Saw that on your IG post, that looks great. Sign making is fun and lasers take all the irritating parts out.
Its been so hot up here (111f) i havent been motivated to do much.
Did cut out and work on a little virtual pinball test bench to see if i can get it working before moving to a more solid setup:
View attachment 20534View attachment 20535

Also played music for the first time in front of people, went well.
View attachment 20533

Can I request some Slayer covers?

 

[Doc J]

I'm making a sparkling carbonated water station. We have great water where I live which is a gated commuity with a private well, but sparkling water is my favourite. So instead of buying cases and cases of San Pellegrino or Perrier I can make my own whenever I want.

Those CO2 bottles are firetrucking heavy, so I made a safety trolley to move mine around more easily.

The appliance of Science - always good!

Doc...shhhhhh!

 

[Yotaman1985]

Got to maiden my EA BDXs jet this weekend. Flew fantastic and really looking forward to putting more flights on it. Short video of my first landing